The present invention relates to an ink-jet head and a recording apparatus.
One of conventionally known inkjet heads includes a pressure chamber charged with an ink, an ink supplying passage communicated with the pressure chamber for supplying the ink to the pressure chamber, a nozzle communicated with the pressure chamber through an ink discharging passage, and pressure applying means (an actuator) for applying a pressure to the pressure chamber. In such an ink-jet head, the pressure is applied to the pressure chamber by the pressure applying means, so as to discharge the ink charged in the pressure chamber from the nozzle.
In this ink-jet head, meniscus vibration is caused at the tip opening of the nozzle when the ink is discharged. Pressure waves caused by the vibration are propagated from the pressure chamber to the ink supplying passage. The pressure waves propagated to the ink supplying passage are also propagated to another pressure chamber communicated with this ink supplying passage, so that the ink may be discharged from another nozzle communicated with this other pressure chamber.
As a countermeasure, for example, Japanese Laid-Open Patent Publication No. 9-314836 discloses an ink-jet head including a damper wall as a top wall of an ink supplying passage. In this ink-jet head, an air chamber is provided in a position opposing an ink supplying passage, and a partition wall between the ink supplying passage and the air chamber is made from a flexible damper wall. Thus, when the pressure waves caused as described above are propagated to the ink supplying passage, the damper wall absorbs and eliminates the pressure waves. Therefore, the propagation of the pressure waves to another pressure chamber is avoided, so that an ink can be prevented from being discharged from another nozzle.
Such an ink-jet head is fabricated by jointing a plurality of stacked plate materials with one another. Also, the air chamber is a space enclosed with the damper wall. Therefore, the pressure within the air chamber is increased through heating performed in fabricating the ink-jet head and is lowered thereafter due to decrease of the temperature. As a result, in a completed ink-jet head, the damper wall remains to be deformed due to the pressure difference between the ink supplying passage and the air chamber. When the damper wall is thus deformed, the pressure waves propagated through the ink cannot be absorbed.
Furthermore, since the air chamber is an enclosed space, the air within the air chamber is expanded and shrunk in accordance with the ambient temperature change during the operation of the inkjet head. Therefore, the pressure within the air chamber is varied. As a result, the characteristic of the damper wall is varied, so that the pressure waves propagated through the ink supplying passage may not be definitely absorbed by the damper wall.